Susceptibility patterns of Escherichia coli: prevalence of multidrug-resistant isolates and extended spectrum beta-lactamase phenotype.

OBJECTIVE

To study Escherichia coli (E. coli) susceptibility, prevalence of multidrug-resistant isolates and possible role of extended spectrum beta-lactamases (ESBL) in E. coli resistance.

SETTING

Department of Medicine, Shifa College of Medicine, Islamabad.

METHODS

Three hundred and seventy eight E. coli isolates from different sources were identified during six-month period. Susceptibility to various antibiotics was checked using standard methods. Multidrug-resistant isolates were separated. Isolates resistant to cefpodoxime and aztreonam were considered as ESBL phenotype, indicating ESBL production.

RESULTS

Most of isolates were resistant to ampicillin and trimethoprim/sulfamethoxazole. Overall resistance to ciprofloxacin, ceftriaxone, cefotaxime and cefpodoxime was 49%, 34%, 36% and 38% respectively. Resistance to fourth generation cephalosporins was lower. Almost all Isolates were sensitive to amikacin, imipenem and tazobactam. Aztreonam resistance was found in 25% isolates. Similar pattern was observed for urinary E. coli isolates; 45% E. coli isolates were found to be multidrug-resistant. Nitrofurantoin showed low-level resistance both to multidrug-resistant as well as urinary isolates. Resistance to both cefpodoxime and aztreonam was found in 25% isolates suggesting ESBL production.

CONCLUSION

E. coli resistance in Pakistan is much higher than reported from western literature. Multidrug-resistant isolates, including third generation cephalosporins and quinolones, are very common. ESBL production may contribute to this high level resistance against beta-lactams.